Semiconductor devices are widely used in a large number of electronic devices, such as computers, cell phones, and others. Semiconductor devices include integrated circuits that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits (ICs). With dimension scaling down to increase integration density of the ICs, requirements in the processing and manufacturing of semiconductor device have become more complex for providing the ICs with multi-functions and advanced performances.
To address the issues in the increase of manufacturing complexity and the accompanied problems in manufacturing processes, it is necessary to advance IC processing and manufacturing. For example, vertical transistors, e.g., a fin field-effect transistor (FinFET), were applied with the same gate length in the semiconductor devices but higher integration density in view of typical planar transistors. However, gate length and channel length of the vertical transistor are much less than that of the horizontal transistor, which increases leakage current and significantly reduce reliability. Further improvements are constantly necessary to satisfy the performance requirement of semiconductor devices.